1. Field of the Invention
The present invention relates to a heat dissipation structure of a multilayer print circuit board.
2. Description of the Related Art
In recent years, due to miniaturization and high density packaging of electronic apparatus, heat generation density of an electronic device is increased and the temperature within the electronic device becomes higher than ever before. In order to prevent the temperature from exceeding a permissible temperature range of electronic components in the electronic device, techniques for efficiently dissipating heat from heat generating components have been proposed.
For example, the Japanese Laid-Open Patent Publication JP 2001-168476 discloses a heat dissipation structure with a plurality of through holes which are bored in an area in contact with a heat generating element on an print circuit board, a conductive plating which is applied to inside wall of each through hole, and a heat dissipation element which is equipped with a plurality of holes bored on the rear surface of the print circuit board. The contact area and the through holes are filled with solder and the heat dissipation element is soldered to the through holes.
The Japanese Laid-Open Patent Publication JP 2005-158914 discloses another heat dissipation structure with a heat dissipation pattern formed on a print circuit board to contact heat dissipation pads of an integrated circuit (IC) package, and one or more through holes which are bored through the heat dissipation pattern in this heat dissipation structure and the through holes are filled with a heat conductor like solder.
With the heat dissipation structure which employs through holes as disclosed in both publications JP 2001-168476 and JP 2005-158914, there is a danger of a solder shortage caused by solder leaking, like a cream solder which is described later, leaking out of the through holes when the circuit board is processed in a solder reflow furnace. Therefore, with the heat dissipation structures disclosed in the abovementioned patent publications, a probability for causing a faulty electric connection of electronic components and solder cracks increases due to the solder shortage.
In view of the problem involved, it is an object of the present invention to provide a heat dissipation structure for a print circuit board to improve heat dissipation efficiency while retaining a necessary soldering strength.